The properties of nanostructures differ from those of bulk materials. Hence, when designing opto-electronic materials, it is often desirable to use nano-structured materials (nano-dots, nano-wires, or nano-wells) to optimize for performance. However, macroscopic devices with nano-materials inherently consist of more than one material. Hence, if only one of the materials is useful for device operation, the effective or useful volume of the device is smaller than the actual volume of the device, since the non-active material takes up volume as well.
Light and electromagnetic fields travel through a material in a way which depends on the material's complex index of refraction. Others have adjusted the surrounding inactive material near the active material in order to increase the absorption of light in the active material. For example, the index of refraction of the incidence medium may be chosen to be large relative to the sample, thus increasing the optical absorption in the sample. (T. Lummerstorfer et al., Analytical and Bioanalytical Chemistry, vol. 388, pp. 55-64 (2007).)